Dishwasher appliances generally include a tub that defines a wash chamber. Rack assemblies can be mounted within the wash chamber of the tub for receipt of articles for washing. Wash fluid (e.g., various combinations of water and detergent along with optional additives) may be introduced into the tub where it collects in a sump space at the bottom of the wash chamber. During wash and rinse cycles, a circulation or wash pump may be used to pump wash fluid to spray assemblies within the wash chamber that can apply or direct wash fluid towards articles disposed within the rack assemblies in order to clean such articles. A drain pump may periodically discharge soiled wash fluid that collects in the sump space and the process may be repeated.
Conventional dishwasher appliances use two separate motors to operate the wash pump and the drain pump. However, additional motors take up more space, add cost, and require additional seals, thus increasing the likelihood of leaks and decreasing appliance reliability. Certain dishwasher appliances have eliminated the need for a second motor by using a single motor and a common drive shaft to rotate a wash pump impeller and a drain pump impeller. However, for a dishwasher appliance which utilizes 100% filtration, i.e., a filtration system in which all of the wash fluid is strained through a filter, the filter typically separates the wash pump impeller and drain pump impeller. As a result, the common drive shaft must pass through the filter, creating a leak path through which food soil and contaminants may pass through the filter.
Accordingly, a dishwasher appliance that utilizes a single motor and common drive shaft to rotate a wash pump and a drain pump while reducing the likelihood of leaks would be useful.